Personality theory was developed by Carl Gustav Jung (1875-1961), expanded by Katharine Cook Briggs (1875-1968) and Isabel Briggs Myers (1896-1980), and further fleshed out by the likes of David Keirsey, Lenore Thomson, and Naomi Quenk.

When the mind is working, it's always working in one of two roles: it is either Perceiving or Judging.

There are two different processes by which one can Perceive:

Sensing

iNtuition

And two different processes by which one can Judge:

Thinking

Feeling

Each of the four processes (Sensing, iNtuition, Thinking, and Feeling) must be applied in a particular domain:

The Introverted domain is the internal world of ideas and emotions.

The Extroverted domain is the external world of people and actions.

All people have all four processes (Thinking, Feeling, iNtuition, and Sensing), but have different preferences for how often and in which domain (Introverted or Extroverted) they use them. A process (T, F, N, and S) used in a particular domain (I or E) is called a function. If one uses the Sensing process in the Extroverted domain, one is using the Extroverted Sensing function, which is denoted as Se. There are eight functions:

Se - Extroverted Sensing

Si - Introverted Sensing

Fe - Extroverted Feeling

Fi - Introverted Feeling

Ne - Extroverted iNtuition

Ni - Introverted iNtuition

Te - Extroverted Thinking

Ti - Introverted Thinking

One's most preferred function is called one's dominant function; one's second most preferred is the auxiliary function; the third is the tertiary function; and the last is the inferior function.

Perceiving and Judging functions always support each other, as do Introverted and Extroverted functions. If one's dominant function is a Perceiving function, one's auxiliary function will be a Judging function, and vice-versa. If one's dominant function is an Introverted function, one's auxiliary function will be an Extroverted function, and vice-versa. So if one's dominant function is Extroverted Sensing (Se) (a Perceiving function), one's auxiliary function must be an Introverted Judging function--either Introverted Thinking (Ti) or Introverted Feeling (Fi). This forms the dominant/auxiliary pair. There are sixteen possible pairs:

The tertiary function plays the same role (Perceiving or Judging) as the auxiliary function but is the alternate process in that role, and in the opposite domain. For instance, if one's auxiliary function is Fi, one's tertiary function is Te.

The inferior function plays the same role as the dominant but is the alternate process in that role, and in the opposite domain. For instance, if one's dominant is Se, one's inferior is Ni. In this fashion, each person has each process, as well a Judging and a Perceiving function in each domain. There are sixteen possible combinations (which are the sixteen personality types).

Note that since one can deduce what the tertiary and inferior functions are from knowledge of what the dominant and auxiliary functions are, the tertiary and inferior do not need to be written, and that the above list simply explicitly lists what the dominant/auxiliary pair list already implied.

One's type is denoted by four letters such as ENFP (which means the same thing as NeFi) or ISTJ (which means the same thing as SiTe).

The first letter denotes the domain of one's dominant function (Extraverted for ENFP and Introverted for ISTJ).

The second letter denotes one's preferred Perceiving process (iNtuition for ENFP and Sensing for ISTJ).

The third letter denotes one's preferred Judging process (Feeling for ENFP and Thinking for ISTJ).

The fourth letter denotes which of one's two preferred processes is Extroverted (the Perceiving one for ENFP and the Judging one for ISTJ).

TiNeSiFe - INTP

NiTeFiSe - INTJ

NeTiFeSi - ENTP

TeNiSeFi - ENTJ

FiNeSiTe - INFP

NiFeTiSe - INFJ

NeFiTeSi - ENFP

FeNiSeTi - ENFJ

TiSeNiFe - ISTP

SiTeFiNe - ISTJ

SeTiFeNi - ESTP

TeSiNeFi - ESTJ

FiSeNiTe - ISFP

SiFeTiNe - ISFJ

SeFiTeNi - ESFP

FeSiNeTi - ESFJ

Thinking of NeFi as ENFP, of SiTe as ISTJ, etc. makes certain behavioral differences among persons of those types easier to access conceptually in practical thinking.

An extroverted dominant function (E) implies greater comfort with self-expression and engaging the world, while an introverted dominant function (I) implies greater comfort with self-reflection and understanding the world.

A preference for intuition (N) implies greater comfort dealing with possibilities and abstractions, while a preference for sensing (S) implies greater comfort dealing with actualities and concretes.

A preference for thinking (T) implies greater interest in impersonal systems, while a preference for feeling (F) implies greater interest in people.

However, the best way to know which types to search for is to learn about the different types, type the people around you, and observe the natures of your relationships. Personality type alone does not guarantee a successful or an unsuccessful relationship. It is merely one important factor out of many.

There are two sets of keywords: positives and negatives. To view and edit these keywords, go to your profile.

If you are interested in politics and care about your match being interested in politics too, but are indifferent to sports and don't want your match to expect you to be interested, you would enter "politics" as a keyword in the positives keyword set, and "sports" in the negatives keywords set. This would match you higher with someone who has an interest in politics, and it would match you lower with someone who has an interest in sports or who doesn't want you to expect an interest in politics from them.

If you're interested in politics, you might have some views which you want your match to agree with. You can use keywords to test for that as well. If you are a libertarian, you would enter "libertarianism" under positives and "communism" under negatives. This way, not only are you being matched on the basis of a shared interest in politics, but also on the basis of shared opinions within the realm of politics. However, if you're indifferent to sports, presumably you won't care which sports team your match loves, so you won't enter any sports teams.

Note that it's not a good idea to enter character traits, such as "honesty" and "dishonesty", which are generally judged the same way by everyone. No one will enter "honesty" in negatives or "dishonesty" in positives, so you're not significantly narrowing your search with those keywords.

Keyword weights control the relative importance of your keywords when searching. The higher the weight you assign to a keyword, the more it will increase or decrease the estimated compatibility of your matches. If you assign the weight of 10 to "reading" and only give 2 to "poetry," "reading" will be considered five times more important than "poetry." The highest weight you can assign is 250.

If the other user entered a keyword in positives which you also entered, then that keyword will show up in green, and the weight you assigned to that keyword will be in parenthesis next to the keyword. If the other user entered a keyword in the opposite set of keywords than you (i.e., you entered "politics" in positives and the other user entered it in negatives), then the keyword will be shown in red, again with weight in parenthesis.

If the match shared negatives option is disabled, shared negatives will be displayed in black, with no weight in parenthesis. If the option is enabled, shared negatives will be displayed same as shared positives.

If the "Match shared negatives" option is disabled (as by default), then the search will only match your positives with other users' positives, your positives with others' negatives, and your negatives with their positives, but it will not match your negatives with their negatives. The reasoning behind this is that shared dislikes aren't as important as shared likes. You will still see all shared negatives when viewing a person's profile--they just won't be reflected in the match score. If you do want to match shared negatives, you can turn on the option in the Search Settings.

If you choose to restrict keywords, other users will be able to see only those of your keywords which they entered as well. If you don't choose to restrict keywords, other users will see all of your keywords (assuming TypeTango has approved them).